68 Re-entrant Angles. I lfl j r It is a general law that there should be no abrupt corners in a casting, either external or internal, principally for the reasons . 74. - £/V TRA NT A NGL.ES. 1111' = 1 = 11 i'llll Iff i , , i 2 } t zz. already given, and also to permit of an easy flow of the metal, and prevent the breakage of corners of sand.